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From: gallagher@husc4.UUCP
Newsgroups: sci.bio
Subject: Re: Life Classification
Message-ID: <1991@husc6.UUCP>
Date: Fri, 15-May-87 08:48:14 EDT
Article-I.D.: husc6.1991
Posted: Fri May 15 08:48:14 1987
Date-Received: Sat, 16-May-87 14:53:52 EDT
References: <9543@duke.cs.duke.edu> <1125@ius2.cs.cmu.edu>
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Reply-To: gallagher@husc4.UUCP (paul gallagher)
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In article <396@its63b.ed.ac.uk> simon@its63b.ed.ac.uk (ECSC68 S Brown CS) writes:
>
>I can't remember what the fundamental differance between the eukaryotes
>and the prokaryotes is, or even if there really is one at all! I do remember
>that all the prokaryotes are haploid, so it would be very nice and convenient
>if the eukaryotes were all diploid, wouldn't it? Anyone know anything about
>any of this?
>
>----------------------------------
>| Simon Brown 		         | UUCP:  seismo!mcvax!ukc!{its63b,cstvax}!simon


Prokayotes and eukaryotes are very different.  The most obvious difference is
that eukaryotes possess a discrete nucleus (eu-caryon = true nucleus), while
prokaryotes do not.  Also, prokaryotes have only 1 chromosome, without histones,
while eukaryotes have more than 1 chromosome, with histones.  Prokaryotes do
not have a nucleolus, endoplasmic reticulum, golgi apparatus, mitochondria,
lysosomes, or microtubules, while all eukaryotes do. Prokaryotes have ribosomes
that are 70 S long, while eukaryotes have 80 S ribosomes (except in their
mitochondria and chloroplasts).  Prokaryotes exchange genetic information
with plasmids, while eukaryotes do it by gamete fusion.  Electron transport
takes place in the cell membrane of prokaryotes, while it takes place in the
organelle membranes of eukaryotes.  There are many other differences.  The
difference between prokaryotes and eukaryotes is probably the most basic
difference among living things.

Prokaryotes are often divided into two kingdoms: Eubacteria and Archebacteria.
Some people may recognize other kingdoms as well.  
Unfortunately, I'm not too familiar with bacteria, but a good place to look
would be in books by Lynn Margulis, a BU professor who studies them.
I think it is believed that the Progenotes - the ancestral cells - gave rise
to the Archebacteria, Eubacteria, and the Urkaryotes (a completely extinct
kingdom).  Apparently, eubacteria started living inside urkaryotes and this
was the first eukaryote (or protist).  This is known as the "endosymbiotic
hypothesis."  The mitochondria and perhaps the nucleus of the eukaryotic cell
are thus the descendants of eubacteria, and the cytoplasm of the cell is the
descendant of urkaryotes.  Later, another eubacterium containg chlorophyll
started living inside the cell, and this became the chloroplast of 
photosynthetic protists and plants.


Paul Gallagher